In the event of a power outage, an analogue power socket timer switch will simply turn off. When then power returns, the unit is not aware of how long the power has been out for and the timer will continue from when the power cut.

If a digital timer is used, on power being restored, the time should be correct with your on/off schedule preserved.

When using a Linux system (Raspberry Pi) and Cron to set a scheduled task, if a power cut occurred within the time an action was supposed to initiate, this window will be missed as when the system power is restored the action event would have passed and won’t be initiated until the next scheduled time.

For the ARPIC or Linux system to act like a 7 day digital timer a script is used on start up to check the time.

Once you have followed the above steps you should have a working temperature probe, that’s great.. but what can you do with it now!?

For the piTank/piGrow projects, I started off by just using the script provide in the instructions above, modifying it slightly and using that to display the temperature value on the piTank web-page. Using some JavaScript you can make the box’s refresh every x seconds, running the probe read script and showing a new value without the need for a page reload. I call this a ‘live’ reading.

Windows 7

Windows 7 systems benefit from using the full set of NTP servers, but cannot be configured to obtain NTP server information from DHCP. Because the control panel does not allow setting multiple servers, settings on these systems must be verified and changed from a command prompt. Systems which are members of the SCS domain will receive NTP configuration via domain group policy and should not be reconfigured.